Through the memoir, Haig references the way societal perceptions of mental illness and people’s general experience with it has shifted over time. In Chapter 17, he refers to the outdated name for depression, “melancholia,” and suggests this was a more uncommon disease—or more uncommonly diagnosed—than contemporary depression as we know it today.

Despite its prevalence in modern society, depression and other forms of mental illness have existed since ancient times, with written accounts dating back to 2000 BCE, four thousand years ago. In this time, depression was considered a spiritual illness instilled by malignant or demonic forces. This belief led to brutal treatments in an effort to drive away spiritual forces, often leaving the patient worse off than they were before.

It wasn’t until around 400 BCE that another perspective began to emerge. This was put forth by Hippocrates, often referred to as the father of modern medicine. He established a system of humors, or bodily fluids, which influenced a person’s behavior: yellow bile, black bile, phlegm, and blood. People with an excess of any one of these humors would be considered choleric, melancholic, phlegmatic, or sanguine, and each state was associated with certain personality traits.